Form component that allows the user to select multiple files to upload via a single <input
type="file"/> field.
Notice that this component clears its model at the end of the request, so the uploaded files MUST
be processed within the request they were uploaded.
Uses javascript implementation from
http://the-stickman.com/web-development/javascript/upload-multiple
-files-with-a-single-file-element/
For customizing caption text see RESOURCE_LIMITED and RESOURCE_UNLIMITED
For an example of styling using CSS see the upload example in wicket-examples

renderHead(IHeaderResponse response)
Render to the web response whatever the component wants to contribute to the head section.

void

updateModel()
Updates this components model from the request, it expects that the object is already
converted through the convertInput() call that is called by the validate() method when a form
is being processed.

UNLIMITED

RESOURCE_LIMITED

Resource key used to retrieve caption message for when a limit on the number of uploads is
specified. The limit is represented via ${max} variable.
Example: org.apache.wicket.mfu.caption.limited=Files (maximum ${max}):

onBeforeRender

NOTE: If you override this, you *must* call super.onBeforeRender() within
your implementation.
Because this method is responsible for cascading Component.onBeforeRender() call to its
children it is strongly recommended that super call is made at the end of the override.

convertValue

Subclasses should overwrite this if the conversion is not done through the type field and the
IConverter. WARNING: this method may be removed in future versions.
If conversion fails then a ConversionException should be thrown

updateModel

Updates this components model from the request, it expects that the object is already
converted through the convertInput() call that is called by the validate() method when a form
is being processed.
By default it just does this:

setModelObject(getConvertedInput());

DO NOT CALL THIS METHOD DIRECTLY UNLESS YOU ARE SURE WHAT YOU ARE DOING. USUALLY UPDATING
YOUR MODEL IS HANDLED BY THE FORM, NOT DIRECTLY BY YOU.